In many industries, there is a need to control the volume of entrapped gas in a variety of materials so that more desirable products may be achieved. The terms "entrapped gas" are herein intended to mean the volume of gas which is entrapped or entrained within a substrate in a material or sample. Furthermore, the terms "material" or "sample" are herein intended to consist of: (1) a substrate, such as a liquid, solid, or semi-solid; and (2) entrapped gas which is a gas that is in a gaseous state and not dissolved within the substrate. Therefore, in simplified terms, entrapped gas means "bubbles" of gas which are trapped within the substrate of a material sample, which bubbles may have a volume or size ranging from visible to microscopic or sub-microscopic.
Examples of known uses for measuring entrapped gas in products are many. For example, in an industrial setting it is believed that the durability of concrete may be increased by controlling the amount of entrapped gas to a predetermined level within a concrete substrate prior to setting. In another example, various consumer goods are also believed to rely in part upon controlling the amount of entrapped gas in order to be sold and used in a reliable and consistent condition. Such consumer goods may include, without limitation: creams and ointments, such as for use in beauty care; pastes, such as toothpaste; or various food substances, such as for example whipped cream. In still a further example, various medical products also require the ability to control the volume of entrapped gas within a particular substrate in order to achieve a reliable, safe product which provides an intended result during use. Further more specific examples of such medical products include, without limitation: pharmaceuticals; and medical creams, gels, and ointments.
Furthermore, the ability to control the gas content in a material is closely related to, and in fact largely dependent upon, the ability to measure the entrapped gas volume in the overall material. Therefore, the ability to measure the entrapped gas volume may be of paramount importance in the quality control of producing such materials.
In one respect, measurement of entrapped gas volume may provide indicia of certain qualities of the overall material sample. For example, the porosity of a sample is a direct consequence of the entrapped gas volume within the sample and the determination of porosity of certain materials is often desirable. In another example, for materials such as cement, sand, gravel, and other admixtures and aggregates, it is believed that the specific gravity and moisture content of the overall sample can be assessed at least in part based upon the known volume of entrapped gas.
In another respect, measurement of entrapped gas volume may also provide for the determination of specific properties of the substrate within the sample, such as substrate volume and density. It is believed that accurate determination of the density and volume of a substrate in a material sample may facilitate the production for certain types of materials. For example, density determinations can be used as a diagnostic tool for identifying purity of the substances which form the substrate or for indicating adulterations in preparation of known compositions. Further to this need, measurement of entrapped gas volume may provide for a direct determination of substrate volume, and therefore substrate density. Substrate volume may be calculated by subtracting entrapped gas volume from the overall sample volume. Thereafter, substrate density may determined by multiplying the substrate volume by the substrate mass.